Distributed Antenna System, Allocation of Distributed Antennas, Base Station

1. A distributed antenna system, comprising: a plurality of antennas; and a base station for transmitting or receiving a signal by the antennas, forming a plurality of antenna groups, and deciding a single antenna or antennas that form the each antenna group; wherein when an other base station other than the base station included in the distributed antenna system provides a time or frequency at which a transmitted power is reduced or zero among of time or frequency resources, the base station estimates the antennas in a communication area of each mobile station using received powers of an uplink reference signal transmitted by each mobile station, calculates interference powers from the other base station to the mobile stations in the communication area of the antennas based on received powers of a downlink reference signal transmitted from the other base station that respective mobile stations report, calculates a first interference power from the other base station to the communication area of respective antennas by averaging the interference powers from the other base station that the mobile stations report, decentralizes a single or a plurality of antennas at which the first interference power is relatively high into different antenna groups according to magnitudes of the calculated first interference power, and decides the antennas that form the antenna group by combining the antenna(s) with a single antenna or antennas at which the first interference power is relatively low.

2. The distributed antenna system according to claim 1 , wherein the base station acquires the first interference power for each antenna, selects a first antenna with which the first interference power becomes a maximum or more than or equal to a previously set threshold, selects a second antenna with which a second interference power arising between the antennas connected to the base station becomes a maximum or more than or equal to a previously set threshold, allocates the same antenna group to the selected first and second antennas, and decides the antenna group for a plurality of antennas in the system by repeating the selection of the first antenna, the selection of the second antenna, and the allocation of the antenna group and for each antenna.

3. The distributed antenna system according to claim 2 , wherein the base station measures a received power of the uplink reference signal for each antenna received by the each antenna, receives a report of the uplink transmitted power of the mobile station or a difference between a maximum transmitted power of the mobile station and a current transmitted power from the each mobile station, calculates the downlink received power at the each mobile station from the received power of the uplink reference signal of the each antenna that was measured and the reported or calculated transmitted power of the each mobile station, finds an average value of the received powers of the signals transmitted from a plurality of other antennas in the communication area of the each antenna, and finds the second interference power among the each antenna and the other antennas.

4. The distributed antenna system according to claim 2 , wherein the second interference power from a plurality of other antennas is previously stored for each antenna.

5. The distributed antenna system according to claim 1 , wherein the base station calculates a second interference power arising among the antennas connected to the base station by averaging the received powers of the downlink reference signal calculated from the received powers of the uplink reference signals that the mobile stations transmit, and forms the antenna group so that a sum of channel capacities of the antenna group that are obtained based on the second interference power, the first interference power, and a ratio of a time or frequency at which the first interference power becomes low may become a maximum or more than or equal to a previously set threshold.

6. The distributed antenna system according to claim 5 , wherein the base station measures the received power of the uplink reference signal received by each antenna for each antenna, receives a report of the uplink transmitted power of the mobile station or a difference between a maximum transmitted power and a current transmitted power of the mobile station, calculates the downlink received power at each mobile station from a received power of the uplink reference signal being measured and the transmitted power of the each mobile station that was reported or calculated, finds an average value of the received powers of the signals transmitted from a plurality of other antennas in the communication area of the each antenna, and finds the second interference power among the each antenna and the other antennas.

7. The distributed antenna system according to claim 5 , wherein the second interference power from a plurality of other antennas is previously stored for each antenna.

8. The distributed antenna system according to claim 1 , wherein the base station calculates a first channel capacity at a time other than Almost Blanc Subframe or a frequency other than Fractional Frequency Reuse of each antenna group that is tentatively decided, calculates a second channel capacity at a time of the Almost Blanc Subframe or frequency of the Fractional Frequency Reuse of each antenna group that is tentatively decided, calculates a sum of the channel capacities of each antenna group in full time in the case of the Almost Blanc Subframe or in full frequencies in the case of the Fractional Frequency Reuse based on the first and second channel capacities, and decides the antenna group for a plurality of antennas in the system by calculating a combination of the antennas in which the sum of the channel capacities becomes a maximum or more than or equal to a previously set threshold for possible combinations of the antenna group and the antennas.

9. The distributed antenna system according to claim 1 , wherein the base station allocates a time resource of Almost Blanc Subframe or a frequency resource of Fractional Frequency Reuse preferentially to a mobile station located in the communication area where the first interference is high, and allocates a time resource other than of the Almost Blanc Subframe or a frequency resource other than of the Fractional Frequency Reuse preferentially to a mobile station located in the communication area where the first interference is low.

10. The distributed antenna system according to claim 1 , wherein the base station acquires Almost Blanc Subframe information from the other base station, receives a report of a communication quality in Almost Blanc Subframe and a communication quality in a time other than the Almost Blanc Subframe, and allocates a time resource of the Almost Blanc Subframe preferentially to a mobile station at which the first interference is high, while allocates a time resource other than of the Almost Blanc Subframe to a mobile station at which the first interference is low.

11. The distributed antenna system according to claim 1 , wherein the base station acquires Fractional Frequency Reuse information from the other base station, receives a report of communication qualities of the Subbands from each mobile station, allocates a Subband in which the first interference power is low preferentially to a mobile station at which the first interference is high, and allocates a Subband other than that Subband preferentially to a mobile station at which the first interference is low.

12. The distributed antenna system according to claim 1 , wherein one antenna group has one cell ID.

13. The distributed antenna system according to claim 1 , wherein the base station comprises: a baseband unit for performing a baseband signal processing of the antenna group that includes a single or a plurality of antennas; a plurality of schedulers for allocating the time or frequency resources to the mobile stations in the antenna group; an antenna group configuration unit that forms a plurality of antenna groups and decides a single or a plurality of antennas that form the each antenna group; and a switch for connecting between the baseband unit and the single antenna or the antennas according to the decided antenna group.

14. A distributed antenna allocation method in a distributed antenna system, wherein the distributed antenna system comprises a plurality of antennas, and a base station for transmitting or receiving a signal from the antennas, forming a plurality of antenna groups, and deciding a single antenna or antennas that form each antenna group, wherein when an other base station other than the base station included in the distributed antenna system provides a time or frequency at which a transmitted power is reduced or zero among of time or frequency resources, the base station estimates the antennas in the communication area of each mobile station using received powers of an uplink reference signal transmitted by each mobile station, calculates interference powers from the other base station to the mobile stations in the communication area of the antennas based on the received powers of a downlink reference signal of the other base station that respective mobile stations report, calculates a first interference power from the other base station to the communication area of the antennas by averaging the interference powers from the other base station that the mobile stations report, decentralizes a single or a plurality of antennas at which the first interference power is relatively high into different antenna groups according to magnitudes of the calculated first interference power, and decides the antennas that form the antenna group by combining the antenna(s) with a single antenna or antennas at which the first interference power is relatively low.

15. A base station in a distributed antenna system, comprising an antenna group configuration unit for transmitting or receiving signals from a plurality of antennas, forming a plurality of antenna groups, and deciding a single antenna or antennas that form the each antenna group, wherein when an other base station other than the base station included in the distributed antenna system provides a time or frequency at which a transmitted power is reduced or zero among of time or frequency resources, the antenna group configuration unit estimates antennas in the communication area of each mobile station using received powers of an uplink reference signal transmitted by each mobile station, calculates interference powers from the other base station to the mobile stations in the communication area of the antennas based on received powers of a downlink reference signal from the other base station that respective mobile stations report, calculates a first interference power from the other base station to the communication area of the respective antennas by averaging the interference powers from the other base station that the mobile stations report, decentralizes a single antenna or antennas at which the first interference power is relatively high into different antenna groups according to magnitudes of the calculated first interference power, and decides the antennas that form the antenna group by combining the antenna(s) with a single antenna or antennas among the antennas at which the first interference powers are lower than the first interference power of the decentralized antennas.